1. Field of the Invention
The present invention is related to a method of controlling minimization of drive test, and more particularly, to a method of activating minimization of drive test in the idle mode.
2. Description of the Prior Art
The 3rd Generation Partnership Project (3GPP) has developed a universal mobile telecommunications system (UMTS) which adopts a wideband code division multiple access (WCDMA) technology capable of providing high frequency spectrum utilization, universal coverage, and high-speed/quality multimedia data transmission. In the UMTS, a radio access network known as a universal terrestrial radio access network (UTRAN) includes multiple base stations, commonly known as Node-Bs (NBs), for communicating with multiple user equipments (UEs). Furthermore, a long-term evolution (LTE) system is now being developed by the 3GPP in order to further improve performance of the UMTS to satisfy users' increasing needs. The LTE system includes a new radio interface and radio network architecture which provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved UTRAN (E-UTRAN) includes multiple evolved NBs (eNBs) for communicating with multiple UEs and a core network which includes a mobility management entity (MME), a serving gateway and other devices for NAS (Non Access Stratum) control.
NBs of the wireless communication system must be deployed properly in order to provide seamless, high quality and large signal coverage without experiencing call drops or signal degradation. However, planning and optimizing the deployment of the NBs are based on signal quality measurements which may be time- and effort-consuming for an operator of the wireless communication system. Common methods of performing the measurements include measuring the signal strength or quality at different time and geographical locations of interest. Therefore, it is more economical for a UE of the wireless communication to perform the measurements and send the measurement report to a NB. Based on the measurement reports received from multiple UEs, the deployment of the NBs may be planned and optimized accordingly without spending many human and material resources. For such measurements, minimization of drive tests (MDTs) which include immediate MDT and logged MDT are defined in corresponding 3GPP specifications.
A UE is configured to perform an immediate MDT in a connected mode, in which reference signal received power (RSRP), reference signal received quality (RSRQ), power headroom (PH), uplink signal strength, or signal to interference and noise ratio (SINR) may be measured. The UE may report the measurement results to a NB serving the UE when a report condition is satisfied.
In order to perform a logged MDT, a UE is configured to receive a logged measurement configuration message from the NB in the connected mode. The logged measurement configuration message is associated with an MDT configuration which includes measurement duration, measurement interval or measurement parameter. After entering an idle mode, the UE is configured to perform a logged MDT according to the logged measurement configuration message and store the measurement result. When the measurement length or the amount of the measurement data exceed a predetermined value, the UE stops performing the logged MDT and sends the measurement result to the NB after switching to the connected mode.
In the prior art when the network requests to activate a specific logged MDT, which is currently not performed by the UE, for some reason, the UE needs to switch to the connected mode for receiving the corresponding instruction from the network. In other words, the NB is unable to directly control the operation of the UE in the idle mode. The UE is constantly required to switch between the connected mode and the idled mode, which may consume more power and waste network resources.